As an avid AS-VAL user, as well as an avid ACR user, I struggle to answer the question.
I use them both for relatively the same purpose, but they seem to go in and out of my loadout depending on the map.
I run the Val with the HD-33, laser, (suppressor), and AFG. I don't figure on the stubby or ergo being much use point blank, where this weapon excels, and at ranges outside of 20m when you will be tap firing the AFG is a better benefit to make up for the high FSM.
I run the ACR with the same setup, HD-33, laser, suppressor, and AFG. For the same reasons.
Now, despite the VAL's higher damage and slightly higher ROF, the TTK is basically the same in both weapons. So the ACR has an clear advantage in a few areas.
- It has an extra 10 rounds making it overall more usable.
- It has one of if not the fastest reload in the whole game for a primary weapon, meaning when it does run empty it is back in the fight in moments. You can afford a little more aggression in your tactics.
- It is a multi-kit weapon, meaning that it's learning curve can be easily translated to other battlefield roles (switching kit does not mean switching weapons).
The VAL, on the other hand, has one distinct advantage over the ACR in that it's hipfire accuracy is about twice as good.
I usually play Domination, so my reference will be to those maps.
Siege of Shanghai and Dawnbreaker, for example, will see me use the ACR. Lots of close quarters fights inside buildings and across streets, with the occasional need to stretch out a bit. Danger in all directions, not a ton of cover to use. Advantage is the ACR for the reload speed and extra 10 rounds for facing the occasional squad.
Dragon Pass and Lost Islands, for example, will see me use the VAL. Tons of "garbage" all over the map that enemies can be waiting around or spring from behind, can be completely CQB if you move about the map properly, and plenty of cover to use. Sudden encounters favor hip-fire, more 1v1 encounters, cover means reload speed isn't as crucial.